Leakage current detection and control for one or more electrically controllable privacy glazing structures

ABSTRACT

An electrical characteristic of a privacy glazing structure and indicative of a health of the privacy glazing structure can be measured at a first time and at a second time later than the first time. In response to detecting a change in the electrical characteristic indicating a change in the health of the privacy glazing structure, one or more parameters of an electrical drive signal can be adjusted to compensate for the change in the health of the privacy glazing structure. The electrical characteristic can be measured at a plurality of times after the second time and compared to the electrical characteristic measured at the first time. If, at any of the plurality of times, the measured electrical characteristic differs from the electrical characteristic measured at the first time by more than a threshold amount, one or more parameters of the electrical drive signal can be adjusted.

RELATED MATTERS

This application claims the benefit of U.S. Provisional PatentApplication No. 62/840,038, filed Apr. 29, 2019, the entire contents ofwhich are incorporated herein by reference.

TECHNICAL FIELD

This disclosure relates to structures that include an electricallycontrollable optically active material and, more particularly, todrivers for controlling the electrically controllable optically activematerial.

BACKGROUND

Windows, doors, partitions, and other structures having controllablelight modulation have been gaining popularity in the marketplace. Thesestructures are commonly referred to as “smart” structures or “privacy”structures for their ability to transform from a transparent state inwhich a user can see through the structure to a private state in whichviewing is inhibited through the structure. For example, smart windowsare being used in high-end automobiles and homes and smart partitionsare being used as walls in office spaces to provide controlled privacyand visual darkening.

A variety of different technologies can be used to provide controlledoptical transmission for a smart structure. For example, electrochromictechnologies, photochromic technologies, thermochromic technologies,suspended particle technologies, and liquid crystal technologies are allbeing used in different smart structure applications to providecontrollable privacy. The technologies generally use an energy source,such as electricity, to transform from a transparent state to a privacystate or vice versa.

In practice, an electrical driver may be used to control or “drive” theoptically active material. The driver may apply or cease applyingelectrical energy to the optically active material to transition betweena transparent state and privacy state, or vice versa. In addition, thedriver may apply an electrical signal to the optically active materialonce transitioned in a particular state to help maintain that state. Forexample, the driver may apply an electrical signal of alternatingpolarity to the optically active material to transition the opticallyactive material between states and/or maintain the optically activematerial in a transitioned stated.

In some cases, one or more changing characteristics in a structureincluding an electrically controllable optically active material rendera previously-suitable electrical drive signal for controlling theoptical state of the structure less suitable for the new characteristicsof the structure. For example, changing electrical and/or chemicalcharacteristics of the structure can change the optical response of thestructure to a given electrical drive signal. This can lead toundesirable and/or unexpected optical properties of the electricallycontrollable optically active material in response to the drive signal.Additionally or alternatively, such changes can lead to operatinginefficiencies, such as electrical inefficiency due to the electricaldrive signal no longer being suitable for the characteristics of thestructure.

SUMMARY

In general, this disclosure is directed to privacy structuresincorporating an electrically controllable optically active materialthat provides controllable privacy. The privacy structures can beimplemented in the form of a window, door, skylight, interior partition,or yet other structure where controllable visible transmittance isdesired. In any case, the privacy structure may be fabricated frommultiple panes of transparent material that include an electricallycontrollable medium between the panes. Each pane of transparent materialcan carry an electrode layer, which may be implemented as a layer ofelectrically conductive and optically transparent material depositedover the pane. The optically active material may be controlled, forexample via an electrical driver communicatively coupled to theelectrode layers, e.g., by controlling the application and/or removal ofelectrical energy to the optically active material. For example, thedriver can control application and/or removal of electrical energy fromthe optically active material, thereby causing the optically activematerial to transition from a scattering state in which visibilitythrough the structure is inhibited to a transparent state in whichvisibility through the structure is comparatively clear.

The electrical driver, which may also be referred to as a controller,may be designed to receive power from a power source, such as arechargeable and/or replaceable battery and/or wall or mains powersource. The electrical driver can condition the electricity receivedfrom the power source, e.g., by changing the frequency, amplitude,waveform, and/or other characteristic of the electricity received fromthe power source. The electrical driver can deliver the conditionedelectrical signal to electrodes that are electrically coupled to theoptically active material. In addition, in response to a user input orother control information, the electrical driver may change theconditioned electrical signal delivered to the electrodes and/or ceasedelivering electricity to the electrodes. Accordingly, the electricaldriver can control the electrical signal delivered to the opticallyactive material, thereby controlling the material to maintain a specificoptical state or to transition from one state (e.g., a transparent stateor scattering state) to another state.

Some aspects of the instant disclosure are directed toward systems andmethods for or otherwise capable of assessing and adapting to changingcharacteristics of an electrically controllable optical privacy glazingstructure. Some aspects of the instant disclosure involve measuring anelectrical characteristic of a privacy glazing structure indicative of ahealth of the privacy glazing structure at a first time and measuringthe electrical characteristic of the privacy glazing structureindicative of the health of the privacy glazing structure at a secondtime later than the first time.

A detected change in the electrical characteristic can indicate a changein the health of a privacy glazing structure. In some embodiments, atleast one parameter of an electrical drive signal provided to theprivacy glazing structure can be adjusted to compensate for the changein the health of the privacy glazing structure. In some examples,adjusting a parameter of the electrical drive signal includes increasinga voltage, decreasing a frequency, pulsing a voltage, or combinationsthereof.

In some examples, a leakage current value associated with a privacyglazing structure can be determined, and adjusting at least oneparameter of the drive signal is performed if the determined leakagecurrent satisfies a predetermined condition.

Additionally or alternatively, the electrical characteristic of theprivacy glazing structure indicative of the health of the privacyglazing structure can be measured at a plurality of additional timeslater than the second time and the measured characteristic at each ofthe plurality of times can be compared to the electrical characteristicmeasured at the first time. In some such examples, if, at any of theplurality of times, the electrical characteristic differs from theelectrical characteristic at the first time by more than a thresholdamount, at least one parameter of the electrical drive signal can beadjusted.

In some examples, observing changes in one or more electricalcharacteristics of a privacy glazing structure can indicate changinghealth conditions of the privacy glazing structure, such as changingchemical or electrical properties (e.g., due to damage or degradation).In some such embodiments, updating the electrical drive signal inresponse to detected changes can help maintain appropriate electricaldrive signals or changing structure characteristics.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a side view of an example privacy glazing structure.

FIG. 2 is a side view of the example privacy glazing structure of FIG. 1incorporated into a multi-pane insulating glazing unit.

FIG. 3 is an exemplary schematic illustration showing an exampleconnection arrangement of a driver to electrode layers of a privacystructure.

FIGS. 4A and 4B show exemplary driver signals applied between a firstelectrode layer and a second electrode layer over time.

FIG. 5 shows an exemplary driver configuration including a switchingnetwork and a plurality of energy storage devices in communicationtherewith.

FIG. 6 shows a driver in communication with a plurality of privacyglazing structures.

FIG. 7 shows an exemplary process-flow diagram illustrating an exemplaryprocess for driving a privacy glazing structure with an electrical drivesignal based on privacy structure characterization.

FIG. 8 shows an exemplary categorization of electrical characterizationsof different privacy glazing structures and corresponding electricaldrive signal parameters.

FIG. 9 shows a process-flow diagram for updating an electrical drivesignal provided to a privacy glazing structure via an electrical driver.

FIGS. and 10A and 10B show exemplary drive signal and resulting responsecurrent signal over time for a privacy glazing structure.

FIGS. 11A and 11B show zoomed-in views of the exemplary current andvoltage signals of FIGS. 10A and 10B, respectively, including differentdisplay scales for ease of display.

FIG. 12 shows a process flow diagram showing an exemplary process fordetermining one or more leakage current values.

FIG. 13 shows a process flow diagram showing an example process forapplying staggered electrical drive signals to a plurality of privacyglazing structures.

FIG. 14 shows an example implementation of applying electrical drivesignals including determined amounts of stagger to a plurality ofprivacy glazing structures.

FIG. 15 shows an example implementation of applying electrical drivesignals including determined amounts of stagger to a plurality ofprivacy glazing structures.

FIGS. 16A-16C show example voltage vs. time profiles for a plurality ofelectrical drive signals used to drive a corresponding plurality ofprivacy glazing structures in a system.

DETAILED DESCRIPTION

In general, the present disclosure is directed to electrical controlsystems, devices, and method for controlling optical structures havingcontrollable light modulation. For example, an optical structure mayinclude an electrically controllable optically active material thatprovides controlled transition between a privacy or scattering state anda visible or transmittance state. An electrical controller, or driver,may be electrically coupled to optically active material throughelectrode layers bounding the optically active material. The electricaldriver may receive power from a power source and condition theelectricity received from the power source, e.g., by changing thefrequency, amplitude, waveform, and/or other characteristic of theelectricity received from the power source. The electrical driver candeliver the conditioned electrical signal to the electrodes. Inaddition, in response to a user input or other control information, theelectrical driver may change the conditioned electrical signal deliveredto the electrodes and/or cease delivering electricity to the electrodes.Accordingly, the electrical driver can control the electrical signaldelivered to the optically active material, thereby controlling thematerial to maintain a specific optical state or to transition from onestate (e.g., a transparent state or scattering state) to another state.

Example electrical driver configurations and electrical control featuresare described in greater detail with FIGS. 3-10. However, FIGS. 1 and 2first describe example privacy structures that may utilize an electricaldriver arrangement and electrical control features as described herein.

FIG. 1 is a side view of an example privacy glazing structure 12 thatincludes a first pane of transparent material 14 and a second pane oftransparent material 16 with a layer of optically active material 18bounded between the two panes of transparent material. The privacyglazing structure 12 also includes a first electrode layer 20 and asecond electrode layer 22. The first electrode layer 20 is carried bythe first pane of transparent material 14 while the second electrodelayer 22 is carried by the second pane of transparent material. Inoperation, electricity supplied through the first and second electrodelayers 20, 22 can control the optically active material 18 to controlvisibility through the privacy glazing structure.

Privacy glazing structure 12 can utilize any suitable privacy materialsfor the layer of optically active material 18. Further, althoughoptically active material 18 is generally illustrated and described asbeing a single layer of material, it should be appreciated that astructure in accordance with the disclosure can have one or more layersof optically active material with the same or varying thicknesses. Ingeneral, optically active material 18 is configured to providecontrollable and reversible optical obscuring and lightening. Opticallyactive material 18 can be an electronically controllable opticallyactive material that changes direct visible transmittance in response tochanges in electrical energy applied to the material.

In one example, optically active material 18 is formed of anelectrochromic material that changes opacity and, hence, lighttransmission properties, in response to voltage changes applied to thematerial. Typical examples of electrochromic materials are WO₃ and MoO₃,which are usually colorless when applied to a substrate in thin layers.An electrochromic layer may change its optical properties by oxidationor reduction processes. For example, in the case of tungsten oxide,protons can move in the electrochromic layer in response to changingvoltage, reducing the tungsten oxide to blue tungsten bronze. Theintensity of coloration is varied by the magnitude of charge applied tothe layer.

In another example, optically active material 18 is formed of a liquidcrystal material. Different types of liquid crystal materials that canbe used as optically active material 18 include polymer dispersed liquidcrystal (PDLC) materials and polymer stabilized cholesteric texture(PSCT) materials. Polymer dispersed liquid crystals usually involvephase separation of nematic liquid crystal from a homogeneous liquidcrystal containing an amount of polymer, sandwiched between electrodelayers 20 and 22. When the electric field is off, the liquid crystalsmay be randomly scattered. This scatters light entering the liquidcrystal and diffuses the transmitted light through the material. When acertain voltage is applied between the two electrode layers, the liquidcrystals may homeotropically align and the liquid crystals increase inoptical transparency, allowing light to transmit through the crystals.

In the case of polymer stabilized cholesteric texture (PSCT) materials,the material can either be a normal mode polymer stabilized cholesterictexture material or a reverse mode polymer stabilized cholesterictexture material. In a normal polymer stabilized cholesteric texturematerial, light is scattered when there is no electrical field appliedto the material. If an electric field is applied to the liquid crystal,it turns to the homeotropic state, causing the liquid crystals toreorient themselves parallel in the direction of the electric field.This causes the liquid crystals to increase in optical transparency andallows light to transmit through the liquid crystal layer. In a reversemode polymer stabilized cholesteric texture material, the liquidcrystals are transparent in the absence of an electric field (e.g., zeroelectric field) but opaque and scattering upon application of anelectric field.

In one example in which the layer of optically active material 18 isimplemented using liquid crystals, the optically active materialincludes liquid crystals and a dichroic dye to provide a guest-hostliquid crystal mode of operation. When so configured, the dichroic dyecan function as a guest compound within the liquid crystal host. Thedichroic dye can be selected so the orientation of the dye moleculesfollows the orientation of the liquid crystal molecules. In someexamples, when an electric field is applied to the optically activematerial 18, there is little to no absorption in the short axis of thedye molecule, and when the electric field is removed from the opticallyactive material, the dye molecules absorb in the long axis. As a result,the dichroic dye molecules can absorb light when the optically activematerial is transitioned to a scattering state. When so configured, theoptically active material may absorb light impinging upon the materialto prevent an observer on one side of privacy glazing structure 12 fromclearly observing activity occurring on the opposite side of thestructure.

When optically active material 18 is implemented using liquid crystals,the optically active material may include liquid crystal moleculeswithin a polymer matrix. The polymer matrix may or may not be cured,resulting in a solid or liquid medium of polymer surrounding liquidcrystal molecules. In addition, in some examples, the optically activematerial 18 may contain spacer beads (e.g., micro-spheres), for examplehaving an average diameter ranging from 3 micrometers to 40 micrometers,to maintain separation between the first pane of transparent material 14and the second pane of transparent material 16.

In another example in which the layer of optically active material 18 isimplemented using a liquid crystal material, the liquid crystal materialturns hazy when transitioned to the privacy state. Such a material mayscatter light impinging upon the material to prevent an observer on oneside of privacy glazing structure 12 from clearly observing activityoccurring on the opposite side of the structure. Such a material maysignificantly reduce regular visible transmittance through the material(which may also be referred to as direct visible transmittance) whileonly minimally reducing total visible transmittance when in the privacystate, as compared to when in the light transmitting state. When usingthese materials, the amount of scattered visible light transmittingthrough the material may increase in the privacy state as compared tothe light transmitting state, compensating for the reduced regularvisible transmittance through the material. Regular or direct visibletransmittance may be considered the transmitted visible light that isnot scattered or redirected through optically active material 18.

Another type of material that can be used as the layer of opticallyactive material 18 is a suspended particle material. Suspended particlematerials are typically dark or opaque in a non-activated state butbecome transparent when a voltage is applied. Other types ofelectrically controllable optically active materials can be utilized asoptically active material 18, and the disclosure is not limited in thisrespect.

Independent of the specific type of material(s) used for the layer ofoptically active material 18, the material can change from a lighttransmissive state in which privacy glazing structure 12 is intended tobe transparent to a privacy state in which visibility through theinsulating glazing unit is intended to be blocked. Optically activematerial 18 may exhibit progressively decreasing direct visibletransmittance when transitioning from a maximum light transmissive stateto a maximum privacy state. Similarly, optically active material 18 mayexhibit progressively increasing direct visible transmittance whentransitioning from a maximum privacy state to a maximum transmissivestate. The speed at which optically active material 18 transitions froma generally transparent transmission state to a generally opaque privacystate may be dictated by a variety of factors, including the specifictype of material selected for optically active material 18, thetemperature of the material, the electrical voltage applied to thematerial, and the like.

To electrically control optically active material 18, privacy glazingstructure 12 in the example of FIG. 1 includes first electrode layer 20and second electrode layer 22. Each electrode layer may be in the formof an electrically conductive coating deposited on or over the surfaceof each respective pane facing the optically active material 18. Forexample, first pane of transparent material 14 may define an innersurface 24A and an outer surface 24B on an opposite side of the pane.Similarly, second pane of transparent material 16 may define an innersurface 26A and an outer surface 26B on an opposite side of the pane.First electrode layer 20 can be deposited over the inner surface 24A ofthe first pane, while second electrode layer 22 can be deposited overthe inner surface 26A of the second pane. The first and second electrodelayers 20, 22 can be deposited directed on the inner surface of arespective pane or one or more intermediate layers, such as a blockerlayer, and be deposited between the inner surface of the pane and theelectrode layer.

Each electrode layer 20, 22 may be an electrically conductive coatingthat is a transparent conductive oxide (“TCO”) coating, such asaluminum-doped zinc oxide and/or tin-doped indium oxide. The transparentconductive oxide coatings can be electrically connected to a powersource through notch structures as described in greater detail below. Insome examples, the transparent conductive coatings forming electrodelayers 20, 22 define wall surfaces of a cavity between first pane oftransparent material 14 and second pane of transparent material 16 whichoptically active material 18 contacts. In other examples, one or moreother coatings may overlay the first and/or second electrode layers 20,22, such as a dielectric overcoat (e.g., silicon oxynitride). In eithercase, first pane of transparent material 14 and second pane oftransparent material 16, as well as any coatings on inner faces 24A, 26Aof the panes can form a cavity or chamber containing optically activematerial 18.

The panes of transparent material forming privacy glazing structure 12,including first pane 14 and second pane 16, and be formed of anysuitable material. Each pane of transparent material may be formed fromthe same material, or at least one of the panes of transparent materialmay be formed of a material different than at least one other of thepanes of transparent material. In some examples, at least one (andoptionally all) the panes of privacy glazing structure 12 are formed ofglass. In other examples, at least one (and optionally all) the privacyglazing structure 12 are formed of plastic such as, e.g., a fluorocarbonplastic, polypropylene, polyethylene, or polyester. When glass is used,the glass may be aluminum borosilicate glass, sodium-lime (e.g.,sodium-lime-silicate) glass, or another type of glass. In addition, theglass may be clear or the glass may be colored, depending on theapplication. Although the glass can be manufactured using differenttechniques, in some examples the glass is manufactured on a float bathline in which molten glass is deposited on a bath of molten tin to shapeand solidify the glass. Such an example glass may be referred to asfloat glass.

In some examples, first pane 14 and/or second pane 16 may be formed frommultiple different types of materials. For example, the substrates maybe formed of a laminated glass, which may include two panes of glassbonded together with a polymer such as polyvinyl butyral. Additionaldetails on privacy glazing substrate arrangements that can be used inthe present disclosure can be found in U.S. patent application Ser. No.15/958,724, titled “HIGH PERFORMANCE PRIVACY GLAZING STRUCTURES” andfiled Apr. 20, 2018, the entire contents of which are incorporatedherein by reference.

Privacy glazing structure 12 can be used in any desired application,including in a door, a window, a wall (e.g., wall partition), a skylightin a residential or commercial building, or in other applications. Tohelp facilitate installation of privacy glazing structure 12, thestructure may include a frame 30 surrounding the exterior perimeter ofthe structure. In different examples, frame 30 may be fabricated fromwood, metal, or a plastic material such a vinyl. Frame 30 may defines achannel 32 that receives and holds the external perimeter edge ofstructure 12.

In the example of FIG. 1, privacy glazing structure 12 is illustrated asa privacy cell formed of two panes of transparent material boundingoptically active material 18. In other configurations, privacy glazingstructure 12 may be incorporated into a multi-pane glazing structurethat include a privacy cell having one or more additional panesseparated by one or more between-pane spaces. FIG. 2 is a side view ofan example configuration in which privacy glazing structure 12 from FIG.1 is incorporated into a multi-pane insulating glazing unit having abetween-pane space.

As shown in the illustrated example of FIG. 2, a multi-pane privacyglazing structure 50 may include privacy glazing structure 12 separatedfrom an additional (e.g., third) pane of transparent material 52 by abetween-pane space 54, for example, by a spacer 56. Spacer 56 may extendaround the entire perimeter of multi-pane privacy glazing structure 50to hermetically seal the between-pane space 54 from gas exchange with asurrounding environment. To minimize thermal exchange across multi-paneprivacy glazing structure 50, between-pane space 54 can be filled withan insulative gas or even evacuated of gas. For example, between-panespace 54 may be filled with an insulative gas such as argon, krypton, orxenon. In such applications, the insulative gas may be mixed with dryair to provide a desired ratio of air to insulative gas, such as 10percent air and 90 percent insulative gas. In other examples,between-pane space 54 may be evacuated so that the between-pane space isat vacuum pressure relative to the pressure of an environmentsurrounding multi-pane privacy glazing structure 50.

Spacer 56 can be any structure that holds opposed substrates in a spacedapart relationship over the service life of multi-pane privacy glazingstructure 50 and seals between-pane space 54 between the opposed panesof material, e.g., so as to inhibit or eliminate gas exchange betweenthe between-pane space and an environment surrounding the unit. Oneexample of a spacer that can be used as spacer 56 is a tubular spacerpositioned between first pane of transparent material 14 and third paneof transparent material 52. The tubular spacer may define a hollow lumenor tube which, in some examples, is filled with desiccant. The tubularspacer may have a first side surface adhered (by a first bead ofsealant) to the outer surface 24B of first pane of transparent material14 and a second side surface adhered (by a second bead of sealant) tothird pane of transparent material 52. A top surface of the tubularspacer can exposed to between-pane space 54 and, in some examples,includes openings that allow gas within the between-pane space tocommunicate with desiccating material inside of the spacer. Such aspacer can be fabricated from aluminum, stainless steel, athermoplastic, or any other suitable material.

Another example of a spacer that can be used as spacer 56 is a spacerformed from a corrugated metal reinforcing sheet surrounded by a sealantcomposition. The corrugated metal reinforcing sheet may be a rigidstructural component that holds first pane of transparent material 14apart from third pane of transparent material 52. In yet anotherexample, spacer 56 may be formed from a foam material surrounded on allsides except a side facing a between-pane space with a metal foil. Asanother example, spacer 56 may be a thermoplastic spacer (TPS) spacerformed by positioning a primary sealant (e.g., adhesive) between firstpane of transparent material 14 and third pane of transparent material52 followed, optionally, by a secondary sealant applied around theperimeter defined between the substrates and the primary sealant. Spacer56 can have other configurations, as will be appreciated by those ofordinary skill in the art.

Depending on application, first patent of transparent material 14,second pane of transparent material 16, and/or third pane of transparentmaterial 52 (when included) may be coated with one or more functionalcoatings to modify the performance of privacy structure. Examplefunctional coatings include, but are not limited to, low-emissivitycoatings, solar control coatings, and photocatalytic coatings. Ingeneral, a low-emissivity coating is a coating that is designed to allownear infrared and visible light to pass through a pane whilesubstantially preventing medium infrared and far infrared radiation frompassing through the panes. A low-emissivity coating may include one ormore layers of infrared-reflection film interposed between two or morelayers of transparent dielectric film. The infrared-reflection film mayinclude a conductive metal like silver, gold, or copper. Aphotocatalytic coating, by contrast, may be a coating that includes aphotocatalyst, such as titanium dioxide. In use, the photocatalyst mayexhibit photoactivity that can help self-clean, or provide lessmaintenance for, the panes.

The electrode layers 20, 22 of privacy glazing structure 12, whetherimplemented alone or in the form of multiple-pane structure with abetween-pane space, can be electrically connected to a driver. Thedriver can provide power and/or control signals to control opticallyactive material 18. In some configurations, wiring is used establishelectrical connection between the driver and each respective electrodelayer. A first wire can provide electrical communication between thedriver and the first electrode layer 20 and a second wire can provideelectrical communication between a driver and the second electrode layer22. In general, the term wiring refers to any flexible electricalconductor, such as a thread of metal optionally covered with aninsulative coating, a flexible printed circuit, a bus bar, or otherelectrical connector facilitating electrical connection to the electrodelayers.

FIG. 3 is a schematic illustration showing an example connectionarrangement between a driver and electrode layers of a privacystructure. In the illustrated example, wires 40 and 42 electricallycouple driver 60 to the first electrode layer 20 and the secondelectrode layer 22, respectively. In some examples, wire 40 and/or wire42 may connect to their respective electrode layers via a conduit orhole in the transparent pane adjacent the electrode layer. In otherconfigurations, wire 40 and/or wire 42 may contact their respectiveelectrode layers at the edge of the privacy structure 12 withoutrequiring wire 40 and/or wire 42 to extend through other sections (e.g.,transparent panes 14, 16) to reach the respective electrode layer(s). Ineither case, driver 60 may be electrically coupled to each of electrodelayers 20 and 22.

In operation, the driver 60 can apply a voltage difference betweenelectrode layers 20 and 22, resulting in an electric field acrossoptically active material 18. The optical properties of the opticallyactive material 18 can be adjusted by applying a voltage across thelayer. In some embodiments, the effect of the voltage on the opticallyactive material 18 is independent on the polarity of the appliedvoltage. For example, in some examples in which optically activematerial 18 comprises liquid crystals that align with an electric fieldbetween electrode layers 20 and 22, the optical result of the crystalalignment is independent of the polarity of the electric field. Forinstance, liquid crystals may align with an electric field in a firstpolarity, and may rotate approximately 180° in the event the polarity ifreversed. However, the optical state of the liquid crystals (e.g., theopacity) in either orientation may be approximately the same.

In some embodiments, optical active material 18 behaves electricallysimilar to a dielectric between the first electrode layer 20 and thesecond electrode layer 22. Accordingly, in some embodiments, the firstelectrode layer 20, the optically active material 18, and the secondelectrode layer 22 together behave similar to a capacitor driven bydriver 60. In various examples, the privacy glazing structure 12 canexhibit additional or alternative electrical properties, such asresistance and inductance, for example, due to the structure itselfand/or other features, such as due to the contact between the driver andthe electrode layers 20, 22 (e.g., contact resistance). Thus, in variousembodiments, the privacy glazing structure 12 electrically coupled todriver 60 may behave similarly to a capacitor, an RC circuit, and RLCcircuit, or the like.

FIG. 4A shows an example alternating current drive signal that may beapplied between first electrode layer 20 and second electrode layer 22over time. It will be appreciated that the signal of FIG. 4A isexemplary and is used for illustrative purposes, and that any variety ofsignals applied from the driver may be used. In the example of FIG. 4A,a voltage signal between the first electrode layer and the secondelectrode layer produced by the driver varies over time between appliedvoltages V_(A) and −V_(A). In other words, in the illustrated example, avoltage of magnitude V_(A) is applied between the first and secondelectrode layers, and the polarity of the applied voltage switches backand forth over time. The optical state (e.g., either transparent oropaque) of optically active layer 18 may be substantially unchangingwhile the voltage is applied to the optically active layer even thoughthe voltage applied to the layer is varying over time. The optical statemay be substantially unchanging in that the unaided human eye may notdetect changes to optically active layer 18 in response to thealternating polarity of the current. However, optically active layer 18may change state (e.g., from transparent to opaque) if the driver stopsdelivering power to the optically active layer.

As shown in the example of FIG. 4A, the voltage does not immediatelyreverse polarity from V_(A) to −V_(A). Instead, the voltage changespolarity over a transition time 70 (shaded). In some examples, asufficiently long transition time may result in an observable transitionof the optically active material from between polarities. For instance,in an exemplary embodiment, liquid crystals in an optically activematerial may align with an electric field to create a substantiallytransparent structure, and become substantially opaque when the electricfield is removed. Thus, when transitioning from V_(A) (transparent) to−V_(A) (transparent), a slow enough transition between V_(A) and −V_(A)may result in an observable optical state (e.g., opaque or partiallyopaque) when −V_(A)<V<V_(A) (e.g., when |V|<<V_(A)). On the other hand afast enough transition between polarities (e.g., from V_(A) to −V_(A))may appear to an observer (e.g., to the naked eye in real time) toresult in no apparent change in the optical state of the opticallyactive material.

FIG. 4B shows another example alternating current drive signal that maybe applied between first electrode layer 20 and second electrode layer22 over time. The drive signal of FIG. 4B includes a substantiallytri-state square wave, having states at V_(A), 0, and −V_(A). As shown,during transition time 72 between V_(A) and −V_(A), the signal has atemporarily held state at 0V. While shown as being much shorter than theduration of the drive signal at V_(A) and −V_(A), in variousembodiments, the amount of time the signal is held at 0V (or anotherthird state value) can be less than, equal to, or greater than theamount of time that the drive signal is held at V_(A) or −V_(A). In someexamples, the amount of time that the drive signal is held at 0V (oranother intermediate state) is short enough so that the optically activematerial does not appear to change optical states.

In some examples, if a particular optical state (e.g., a transparentstate) is to be maintained, switching between polarities that eachcorrespond to that optical state (e.g., between +V_(A) and −V_(A)) canprevent damage to the optically active material. For example, in somecases, a static or direct current voltage applied to an optically activematerial can result in ion plating within the structure, causing opticaldefects in the structure. To avoid this optical deterioration, a driverfor an optically active material (e.g., in an electrically dynamicwindow such as a privacy structure) can be configured to continuouslyswitch between applied polarities of an applied voltage (e.g. V_(A)) inorder to maintain the desired optical state.

One technique for applying a voltage of opposite polarities to a load(e.g., an optically active material) is via a switching network, such asan H-bridge configuration, such as described in U.S. Provisional PatentApplication No. 62/669,005, entitled ELECTRICALLY CONTROLLABLE PRIVACYGLAZING STRUCTURE WITH ENERGY RECAPTURING DRIVER, filed May 9, 2018,which is assigned to the assignee of the instant application and isincorporated by reference in its entirety.

FIG. 5 shows an example driver configuration including a switchingnetwork and a plurality of energy storage devices in communication withthe switching network. In the illustrated example, driver 200 includes apower source 210 shown as applying a voltage V_(A), a ground 220, and aswitching network 230 used to drive load 240, for example, in opposingpolarities. Switching network 230 can include one or more switchingmechanisms capable of selectively electrically connecting anddisconnecting components on either side of the switching mechanism. Invarious embodiments, switching mechanisms can include transistors, suchas metal-oxide-semiconductor field-effect transistors (MOSFETs) or thelike. Power source 210 may be a direct current power source (e.g.,battery), an alternating current power source (e.g., wall or mainspower) or other suitable power source. The drive load 240 may beelectrically controllable optically active material 18 along with firstand second electrode layers 20, 22.

In the example of FIG. 5, switching network 230 includes a firstswitching mechanism SW1 coupled between a first side 235 of a load 240and ground 220 and a second switching mechanism SW2 coupled between asecond side 245 of the load 240 and ground 220. In some examples, anisolating component 224 can selectively prevent or permit current flowfrom switching mechanisms SW1, SW2 to ground 220. Switching network 230further includes a third switching mechanism SW3 coupled between thefirst side 235 of the load 240 and the power source 210 and a fourthswitching mechanism SW4 coupled between the second side 245 of the load240 and the power source 210. It will be appreciated that, as usedherein, being “coupled to” or “coupled between” components implies atleast indirect electrical connection. However, unless otherwise stated,the terms “coupled to” or “coupled between” does not require that the“coupled” components be directly connected to one another.

The driver 200 of FIG. 5 includes first energy storage element SE1,which is shown as being in electrical communication with the third andfourth switching mechanisms, SW3 and SW4, respectively and power source210 on a first side, and ground 220 on another side. Isolating component212 is shown as being positioned to selectively enable or disablecurrent flow between the power source 210 and other components of thedriver 200, such as the first energy storage element SE1 or the thirdand fourth switching mechanisms.

The driver 200 further includes a second energy storage element SE2coupled to the first side 235 of the load 240 and being coupled betweenthe third switching mechanism SW3 and the first switching mechanism SW1.Similarly, the driver includes a third energy storage element SE3coupled to the second side 245 of the load 240 and being coupled betweenthe fourth switching mechanism SW4 and the second switching mechanismSW2.

In various embodiments, energy storage elements can be electrical energystorage elements, such as inductive storage elements, capacitive storageelements, one or more batteries, or the like. In some examples, storageelements SE1, SE2, and SE3 are the same. In other examples, at least oneof SE1, SE2, and SE3 is different from the others. In some embodiments,SE1 comprises a capacitive energy storage element and SE2 and SE3comprise inductive energy storage elements. In some such embodiments,SE2 and SE3 comprise matched inductive energy storage elements.

The driver 200 in FIG. 5 further includes a controller 260 incommunication with the switching network 230. In the illustratedexample, controller 260 is in communication with each of the switchingmechanisms (SW1, SW2, SW3, SW4). Controller 260 can be configured tocontrol switching operation of the switching mechanisms, for example, byopening and closing switching mechanisms to selectively electricallyconnect or disconnect components on either side of each of the switchingmechanisms. In various embodiments, controller 260 can be configured tocontrol switching mechanisms in series and/or in parallel (e.g.,simultaneous switching).

In some examples, the controller 260 is configured to control theswitching mechanisms in order to provide a voltage (e.g., from powersource 210) to load 240, such as an optically active material in anelectrically dynamic window. Further, in some embodiments, thecontroller 260 can be configured to control the switching mechanisms inorder to periodically change the polarity of the voltage applied to theload 240. In some such examples, operation of the switching network canbe performed so that at least some of the energy discharged from theload (e.g., when changing polarities) can be recovered and stored in oneor more energy storage elements SE1, SE2, SE3. Such recovered and storedenergy can be used, for example, to perform subsequent chargingoperations.

As described, in some embodiments, driver 200 further includesadditional components for selectively preventing current flow to variousportions of the driver. For instance, in the illustrated embodiment ofFIG. 5, driver 200 includes isolating component 212 configured toselectively permit current flow between power source 210 and otherportions of the driver. Similarly, driver 200 includes isolatingcomponent 224 configured to selectively permit current flow betweenground 220 and other portions of the driver 200. In some examples,isolating components 212, 224 can be controlled via the controller 260during various phases of driver operation. Isolating components caninclude any of a variety of suitable components for selectivelypermitting and/or preventing current flow between various drivercomponents. For example, in various embodiments, isolating components212, 224 can include switches, transistors (e.g., power MOSFETs), orother components or combinations thereof.

Other possible driver configurations are possible, for example, omittingone or more of the above-referenced features, such as one or more energystorage elements, switches, or the like. For instance, in variousexamples, a driver can be configured output an AC electrical drivesignal without requiring switching elements.

FIG. 6 shows a driver 300 in communication with a plurality of privacyglazing structures 310, 320, 330. In various embodiments, the driver 300can be configured to communicate with privacy glazing structures 310,320, 330 simultaneously, for example, to control operation of aplurality of structures at the same time. Additionally or alternatively,privacy glazing structures 310, 320, 330 can be interchangeably placedin communication with driver 300. For instance, in an exemplaryembodiment, driver 300 can include an electrical interface to which anyof a plurality of privacy glazing structures (e.g., 310, 320, 330) canbe coupled. In some embodiments, the driver 300 can be configured toprovide electrical drive signals to each of the plurality of privacyglazing structures 310, 320, 330 for optically controlling suchstructures.

In some examples, electrical drive signals provided from the driver 300to each privacy glazing structure are limited for safety reasons, forexample, to comply with one or more safety standards. For instance, insome embodiments, electrical drive signals are power limited to satisfyone or more electrical safety standards, such as NEC Class 2. Providingdrive signals that satisfy one or more such safety standards can enablesafe installation by a wide range of people, for example, by enablinginstallation without requiring licensed electricians.

In the illustrated example, each of the privacy glazing structures 310,320, 330 has one or more corresponding temperature sensors, 312, 322,and 332, respectively, that can provide temperature informationregarding the corresponding privacy glazing structure. Temperatureinformation can include, for example, contact temperature information(e.g., surface temperature) or non-contact temperature information(e.g., air temperature). In some examples, such temperature sensors 312,322, 332 can provide such temperature information to driver 300.

However, in some cases, different privacy glazing structures havedifferent electrical properties, for example, due to different sizes,different materials, and the like. As a result, different structures mayrequire different drive signals to operate effectively and/orefficiently. For instance, in some embodiments, a drive signal thatworks well for a given privacy glazing structure may result in pooroptical performance in a different privacy glazing structure due todifferences between the structures.

In some examples, a driver can receive identification information from aprivacy glazing structure, for example, from a memory storage componenton the structure including identification information readable by thedriver. In some such examples, the driver can be configured to read suchidentification information and establish an electrical drive signal(e.g., from a lookup table stored in a memory) for driving theidentified structure. However, while providing a first order estimate onan appropriate drive signal for a given structure, in some cases,variations between similar structures (e.g., due to manufacturingvariability, environmental factors, aging characteristics, for example,due to UV degradation, etc.) can result in different electricalcharacteristics between such similar structures. Thus, even two privacyglazing structures of the same make/model may have differentcharacteristics that can lead to inconsistencies between such structureswhen driven with the same electrical drive signal.

In some embodiments, a driver can be configured to characterize one ormore properties of a privacy glazing structure in communicationtherewith in order to determine one or more drive signal parameterssuitable for driving the privacy glazing structure. For example, in someembodiments, a driver is configured to apply an electrical sensing pulseto a privacy glazing structure and analyze the response of the privacyglazing structure to the electrical sensing pulse. The driver can beconfigured to characterize the privacy glazing structure based on theanalyzed response to the electrical sensing pulse. In some embodiments,the driver can be configured to characterize one or more parameters ofthe privacy glazing structure based on the analyzed response, such asone or more electrical parameters.

FIG. 7 shows an exemplary process-flow diagram illustrating an exemplaryprocess for driving a privacy glazing structure with an electrical drivesignal based on privacy structure characterization. The process includesapplying an electrical sensing pulse to the privacy glazing structure(700).

The method of FIG. 7 further comprises analyzing a response of theprivacy glazing structure to the applied electrical sensing pulse (702).In some examples, the electrical sensing pulse comprises a voltage pulse(e.g., having a known voltage vs. time), and the analyzed responsecomprises measuring a current flowing through the privacy glazingstructure over the time the voltage pulse is applied. Additionally oralternatively, the analyzed response can include a measurement of avoltage or current value at a specific time relative to the applicationof the sensing pulse (e.g., 40 milliseconds after the sensing pulse) ora specific time range (e.g., between 5 and 40 milliseconds after thesensing pulse). In some examples, the time or time period can bedetermined based on measured or estimated electrical parameters, such asa resistance and capacitance value, so that time or time period capturesdata within or over a certain time period relative to the parameters,such as 10 RC time constants. The method further includes determiningone or more electrical characteristics of the privacy structure (704).Such one or more electrical characteristics can include a resistance, acapacitance, an inductance, or any combination thereof. For instance, insome examples, a resistance value corresponds to contact/lead resistanceassociated with applying electrical signals to the electrode layer(s)(e.g., 20, 22). Additionally or alternatively, a capacitance value cancorrespond to the capacitance of the optically active material 18between the electrode layers 20 and 22. After determining the one ormore electrical characteristics, the driver can be configured to loadone or more drive parameters for driving the privacy glazing structure(706). Drive parameters can include one or more electrical drive signalparameters, such as a voltage (e.g., peak voltage), frequency, slewrate, wave shape, duty cycle, or the like.

In some examples, characterizing one or more electrical parameterscomprises determining a resistance value (e.g., an equivalent seriesresistance), a capacitance value, and/or an inductance value associatedwith the privacy glazing structure. In some such examples, the drivercan be configured to generate a representative circuit including the oneor more electrical parameters, such as an RC circuit or an RLC circuit.In some embodiments, loading one or more drive parameters (706) can beperformed based on such determined one or more electrical parameters,for example, based on one or more lookup tables and/or equations.

In some embodiments, loading one or more drive parameters (706)comprises establishing a drive signal. Additionally or alternatively, ifa drive signal is currently in place, loading one or more driveparameters can include adjusting one or more drive parameters of theexisting drive signal. In various examples, adjusting one or moreparameters can include loading a new value for the one or moreparameters, or can include a relative adjustment, such as increasing ordecreasing a value associated with the one or more parameters withrespect to an existing electrical drive signal.

Once the one or more parameters associated with the determined one ormore electrical characteristics are loaded, the driver can be configuredto apply an electrical drive signal that includes the loaded driveparameter(s) to the privacy structure (708).

In some examples, the process of FIG. 7 can be performed at a pluralityof times. In some such examples, the analyzed response to the appliedelectrical sensing pulse (e.g., step 702) can include calculating atime-based value of a response, such as a temporal derivative or runningaverage of a measured response (e.g., resulting voltage or currentvalue). Additionally or alternatively, such response data can befiltered over time, for example, to remove noise, outliers, etc. fromthe data collected over time. Such a time-based value can be used todetermine one or more electrical characteristics of the privacystructure.

In some embodiments, the process shown in FIG. 7 is performed upon astart-up process of a privacy glazing structure, such as during aninitial installation. An installer may connect the driver to a privacyglazing structure, and the driver may perform the method shown in FIG. 7in order to establish and apply an initial drive signal for the privacyglazing structure. Such a process can be initiated manually and/orautomatically. In some examples, the ability of the driver to determineand apply an appropriate electrical drive signal for a privacy glazingstructure eliminates the need for different drivers to drive differenttypes of privacy glazing structures, and enables loading an appropriatedrive signal without requiring expertise of which drive parameters maybe suitable for a given privacy glazing structure.

FIG. 8 shows an exemplary categorization of electrical characterizationsof different privacy glazing structures and corresponding electricaldrive signal parameters. As shown in the exemplary illustration of FIG.8, a structure can be categorized according to a low or high resistancevalue and a low or high capacitance value. In some examples, a drivercan be programmed with threshold values to designate which resistancevalues are “low” and which are “high,” and similarly, which capacitancevalues are “low” and which are “high.”

One category of privacy glazing structure shown in FIG. 8 includes a lowresistance and a low capacitance. Such structures can include, forexample, small structures (e.g., contributing to a low capacitancevalue) having busbar contacts (e.g., contributing to a low resistancevalue). In some cases, low resistance values can lead to large currentspikes when a square wave or other sharp transitioning voltage signal isapplied to the structure. Accordingly, a corresponding electrical drivesignal can include one or more features to mitigate risks of a largecurrent value, such as employing a maximum current regulator, utilizinga slew-rate square wave, and/or a pulse-width modulated (PWM) signal(e.g., from the rail voltage). In some examples, a lower-frequencyelectrical drive signal can be used to minimize average powerconsumption over time. One or more such features can adequately charge asmall capacitive load (e.g., a capacitive electrically controllableoptically active material in a privacy glazing structure) to provideproper aesthetic structure behavior while reducing large current spikes.

Another category of structure in the example of FIG. 8 comprises a lowresistance and high capacitance structure, for example, a largestructure (having a high capacitance value) and busbar contacts(contributing to a low resistance value). Such a structure may also besusceptible to large current spikes due to the low resistance, thoughthe low resistance can facilitate filling the capacitance with chargequickly to provide high quality aesthetics during operation of thestructure. Similar techniques can be employed to reduce the risk ofcurrent spikes, such as a maximum current regulator, a slew-rate squarewave signal, or applying a PWM signal.

Another category of structure according to the example of FIG. 8includes a high resistance and a high capacitance, for example, a largestructure having point contacts (e.g., contributing to a higherresistance value). In some such instances, a large resistance value maylimit current spikes, but also may make it more difficult to fill thecapacitance with charge. Further, since the capacitance is large, it canrequire a large amount of charge to quickly charge the structure forgood aesthetic behavior. Thus, in some examples, an electrical drivesignal can include an overdriven square wave. For instance, in someembodiments, the electrical drive signal comprises a square wave inwhich a portion of the square wave is overdriven. In an exemplaryimplementation, within a square wave pulse, the first half of the pulsemay be applied at a higher voltage than the second half of the pulse inorder to more quickly fill the capacitance of the structure.Additionally or alternatively, a lower frequency waveform can be used inorder to provide additional time for the large capacitance to becharged.

A fourth category of structure according to the example of FIG. 8includes a high resistance and a low capacitance, for example, a smallstructure having point contacts. The high resistance generally willreduce large current spikes, and the small capacitance generally allowsfor a relatively small amount of current necessary to fill thecapacitance with charge to achieve good optical aesthetics. In someexamples, such a structure can operate with a “default” electrical drivesignal. In some embodiments, various electrical parameters can beadjusted and/or implemented to increase operation efficiency, such asincorporating a voltage slew-rate to mitigate excessive current peaksand minimize peak power consumption and/or reducing frequency tomitigate average power consumption.

While shown as two bins for two categories, it will be appreciated thatany number of parameters may be analyzed, and may be distinguishable byany number of bins. For instance, in general, a group of N parameters(in FIG. 8, N=2; resistance and capacitance) can be divided into M bins(in FIG. 8, M=2; low and high) into which the parameter values may fall.Combinations of the characteristics and corresponding bins into whichthey fall can be used to identify (e.g., via equation or lookup table)an appropriate electrical drive signal for driving the privacy glazingstructure having such characteristics.

In some examples, methods similar to that shown in FIG. 7 can berepeated over time. Such methods can be carried out manually orautomatically (e.g., according to a pre-programmed schedule) in order todetermine if a drive signal should be updated based on changes in one ormore electrical characteristics of the privacy glazing structure. Insome such examples, the existing drive signal may be stopped in order toexecute a method similar to that shown in FIG. 7 to determine whether ornot a drive signal should be updated. This can be performed manually oraccording to a schedule, for example, at night, when undesirable opticalcharacteristics that may result from an interruption in operation may gounnoticed. In some such embodiments, various data can be stored inmemory, such as determined characteristics of the privacy glazingstructure based on the response to the applied sensing pulse. In someexamples, characteristics of the privacy glazing structure determined atinstallation to establish an electrical drive signal are associated withan initial time t₀.

FIG. 9 shows a process-flow diagram for updating an electrical drivesignal provided to a privacy glazing structure via an electrical driver.In an exemplary implementation, the method shown in FIG. 9 can beperformed after a driver has been applying an existing drive signal to aprivacy glazing structure. The method of FIG. 9 includes applying anelectrical sensing pulse to a privacy glazing structure at a time t_(n)(900), analyzing the response of the privacy glazing structure to theapplied electrical sensing pulse (902), and determining one or moreelectrical characteristics of the privacy glazing structure at timet_(n) (904). The method includes comparing the determinedcharacteristics at time t_(n) to characteristics determined at aprevious time t_(n-1) (906). If the change in the characteristic(s) attime t_(n) with respect to the characteristic(s) at time t_(n-1) is notgreater than a threshold amount (908), then the driver continues toapply the existing electrical drive signal (910). If the change in thecharacteristic(s) between times t_(n-1) and t_(n) is/are greater than athreshold amount (908), the driver can be configured to load and/orupdate one or more drive parameters to establish an updated electricaldrive signal (912).

In some embodiments, the updated electrical drive signal can bedetermined based on the determined electrical characteristics at timet_(n), similar to loading one or more drive parameters based on thedetermined characteristics as described with respect to FIG. 7.Additionally or alternatively, loading/updating one or more driveparameters to establish the updated electrical drive signal can compriseadjusting one or more drive parameters based on an amount of changedetected for the one or more electrical characteristics.

With respect to FIG. 9, determining whether or not the change(s) in oneor more electrical characteristics between times t_(n-1) and t_(n)is/are greater than a threshold amount can be performed in a variety ofways. In some embodiments, each characteristic(s) includes acorresponding absolute threshold difference that, if surpassed, causes achange in the one or more parameters of the electrical drive signal. Forinstance, in an exemplary embodiment, if a resistance value measured asone of the one or more electrical characteristics changes by more than1000 Ohms, the change is considered to be greater than the threshold.Additionally or alternatively, a change greater than a threshold amountcan correspond to a percentage change in a characteristic. For example,in some embodiments, one or more drive parameters can be updated inresponse to a resistance value increasing by at least 100%. In anotherexample, one or more drive parameters can be updated in response to acapacitance value changing by at least 10%.

In some embodiments, change in each of the one or more parameters overtime can be compared to a corresponding threshold. In some examples, ifany one characteristic differs from its previous value by acorresponding threshold amount, the change in characteristic(s) isconsidered to be greater than the threshold amount, and an updatedelectrical drive signal is established. In other examples, the amount ofchange in each of the one or more characteristics must be greater than acorresponding threshold amount in order for the change to be consideredgreater than a threshold and to update an electrical drive signal. Invarious embodiments, different combinations of electricalcharacteristics (e.g., a subset of a plurality of determinedcharacteristics) can be analyzed to determine whether or not the changein the characteristics is greater than a threshold amount.

In some embodiments, loading/updating one or more drive parameters (912)can be based on additional tracked/measured data 914. Tracked/measureddata 914 can include information such as the age of the privacy glazingstructure, the temperature of the privacy glazing structure, or thelike. In some examples, the driver can be configured to adjust one ormore drive parameters based on such data.

For instance, in an exemplary embodiment, in the event that thechange(s) in one or more electrical characteristics between timest_(n-1) and t_(n) is/are greater than a threshold amount, the driver canbe configured to acquire temperature information (e.g., structure and/orenvironment temperature information) and update the one or more driveparameters based on the temperature information. Temperature informationcan be received, for example, from a contact (e.g., thermocouple) ornon-contact (e.g., infrared) temperature measurement device that outputstemperature information representative of the structure itself.Additionally or alternatively, temperature information can be receivedfrom an ambient temperature sensor. In some examples, one or moretemperature sensors can be associated with each of one or more privacyglazing structures in a privacy system. For example with respect to FIG.6, temperature sensors 312, 322, 332 can be configured to providetemperature information (e.g., contact and/or environmental temperatureinformation) associated with corresponding privacy glazing structures310, 320, 330, respectively.

In addition or alternatively to temperature information, if thechange(s) in one or more electrical characteristics between timest_(n-1) and t_(n) is/are greater than a threshold amount, the driver canbe configured to determine the age of the privacy glazing structure andupdate one or more drive parameters based upon the age of the structure.In some examples, a driver can be configured to flag a structure asaging, for example, when the structure has been in operation for apredetermined amount of time and/or when the electrical characteristicsare representative of an aging structure. Age and/or temperature can beused in addition or alternatively to the determined electricalcharacteristics when determining an updated electrical drive signal.

As described with respect to FIGS. 7 and 9, in various processes, thedriver can be configured to apply an electrical sensing pulse to aprivacy glazing structure for characterizing the structure (e.g.,determining one or more electrical characteristics thereof). In someexamples, the characterizing the structure comprises determining one ormore electrical parameters of the structure, such as a resistance, acapacitance, etc., and in some such examples, comprises determining anequivalent circuit representative of the structure's electricalproperties (e.g., an RC circuit, an RLC circuit, etc.).

In various embodiments, different electrical sensing pulses can be usedto determine such characteristics. For instance, in various examples, anelectrical sensing pulse can include a DC sense pulse, a low frequencydrive signal (e.g., a signal having similar characteristics, such asamplitude or waveform, of a drive signal but having lower frequency), oran operational drive signal (e.g., a currently-implemented drivesignal). In some embodiments, a user may select which type of electricalsensing pulse to use when characterizing a privacy glazing structure.

In some cases, a DC sense pulse can provide the most accuratecharacterization, since the DC signal can be applied over several RCtime constants of the structure. In some embodiments, the DC pulse isapplied to a structure for at least five time constants, but can also beapplied for longer amounts of time, such as for at least 10 timeconstants, at least 100 time constants, at least 1000 time constants, orother values. While the exact value of an RC time constant may not beknown a priori, in some examples, a privacy glazing structure can havean expected range of time constants (e.g., associated with differentstructure sizes, types, etc.) that can be used to determine, forexample, a minimum DC pulse length to increase the likelihood that theDC sense pulse lasts at least a minimum number of time constants. Apotential drawback to a DC sense pulse is that during the pulse, thevisual aesthetics of the privacy glazing structure may degrade. However,this type of electrical sensing pulse can be used during, for example,an installation procedure or when the structure is not in use, atemporary decline in the aesthetic appearance of the structure may beacceptable.

In some examples, an operational drive signal can be used as anelectrical sensing pulse, such as one of the drive signals shown inFIGS. 4A and 4B. In an exemplary embodiment, such a drive signal can beapplied at a frequency of between approximately 45 and 60 Hz. In somesuch examples, such a frequency generally results in pulses that are tooshort to reach several RC time constants for structure characterization,and as a result, may provide a less accurate characterization whencompared to a longer DC sense pulse. However, since the operationaldrive signal doubles as the electrical sensing pulse, no aestheticdegradation occurs during the characterization process. Thus,characterization using the operational drive signal as an electricalsensing pulse can be performed during the daytime when the chances ofbeing viewed are high.

In some cases, a low frequency drive signal can provide a balancebetween the DC sense pulse and the operation drive signal as a sensepulse. For example, in some embodiments, reducing the frequency of thedrive signal provides added time for characterizing the response of theprivacy glazing structure to the signal while not impacting theaesthetics of the privacy glazing structure as severely as a longer DCsense pulse. In some examples, a low frequency drive signal has afrequency range between approximately 5 and 45 Hz. In some cases, thelow frequency drive signal still reduces the aesthetics of the privacyglazing structure, and so may be suitable for applying at night when itis unlikely that the privacy glazing structure will be viewed withtemporarily reduced aesthetics.

In various embodiments, a user may manually initiate a privacy glazingstructure characterization process in which one or more electricalsensing pulses is applied to the privacy glazing structure determiningone or more electrical characteristics of the structure, for example, todetermine or update an electrical drive signal. In some such examples, auser may select from a plurality of available electrical sensing pulsetypes, such as those described elsewhere herein. Additionally oralternatively, in some examples, a driver can be configured toautomatically perform a characterization process, for example, accordingto a predetermined schedule (e.g., once per hour, once per day, once perweek, etc.). In some such examples, a driver can be configured toperform different characterization processes according to when theprocess is carried out. For instance, upon initial installation, adriver can apply a DC sense pulse to initially characterize thestructure and establish an electrical drive signal.

After installation, the driver can be configured to periodically applyan electrical sensing pulse to characterize the structure, for example,to determine if one or more characteristics of the structure havechanged and/or if an electrical drive signal should be updated, such asdescribed with respect to FIG. 9. In some such examples, the driver canbe configured to select an electrical sensing pulse to apply, forinstance, depending on a time of day or other factors. For example, insome embodiments, the driver can be configured to apply a low frequencydrive signal electrical sensing pulse, such as described elsewhereherein, if the electrical sensing pulse is applied during one or morepredetermined intervals, such as when temporary aesthetic degradationmay not be noticed. Outside of the predetermined time intervals, forexample, when temporary aesthetic degradation may be noticed, the drivercan be configured to apply an electrical sensing pulse that is theoperational drive signal to reduce or eliminate the impact on thestructure aesthetics during a characterization process.

In some examples, different update schedules may be implementedaccording to the processing capabilities of the system components usedfor performing the analysis. For instance, in some embodiments, on-boardprocessing components may have limited processing ability, and mayperform such analysis less frequently than a cloud-based processingsystem with greater processing resources.

In some examples, periodic characterization of a privacy glazingstructure over time can be used to track structure operation and agingcharacteristics or to adjust the electrical drive signal to accommodatefor changing characteristics, for example, as described with respect toFIG. 9. In some embodiments, determined one or more electricalcharacteristics captured at a plurality of times can be saved in memory,for example, for comparison (e.g., as described with respect to FIG. 9),trend analysis, etc. In some examples, the driver can be configured toperform statistical analysis of the electrical characteristics over timeand recognize patterns. Patterns can include trending of one or moreelectrical characteristics in a given direction over time (e.g., due tostructure breakdown, etc.), repeating trends (e.g., electricalcharacteristics changing during daylight and nighttime hours or changingover seasons as ambient temperatures change, etc.). In some cases, thedriver can similarly track and/or analyze additional data, such asambient or structure temperature data, and can be configured tocorrelate electrical characteristics with such additional data.

Additionally or alternatively, in some implementations, the driver canbe configured to periodically characterize aspects of the privacyglazing structure at a different rate throughout the life cycle of thestructure. For example, in some cases, the driver characterizes thestructure more frequently shortly after installation while the driverlearns the behavior and/or typical characteristics of the structure, forexample, environmental impacts (e.g., temperature, sunlight, etc.) onstructure behavior.

In some examples, the driver can be configured to detect or predict anenvironmental change (e.g., a temperature change, a change in ambientlight, etc.), and can characterize the structure within a short timespan (e.g., within minutes or hours) to isolate impacts of certainfactors. For example, a driver can be configured to characterize astructure when the sun is blocked by a cloud and then again once the sunis no longer blocked in order to isolate the impact of daylight on thestructure characteristics. The driver can be configured to detect suchchanges, for example, via one or more sensors and/or via data analysis(e.g., via internet access to weather data).

Similarly, in an example implementation, a driver can be configured todetect and/or predict an earthquake (e.g., via internet connectivity toan earthquake notification system and/or one or more accelerometers orother sensors). The driver can be configured to characterize thestructure after a detected earthquake to assess for damage or changingoperating characteristics. If the driver receives information (e.g.,from a notification system) that an earthquake is imminent, the drivercan characterize the structure prior to the occurrence of the earthquakeand again after the earthquake to specifically detect changes instructure characteristics due to the earthquake.

In some embodiments, the driver can be configured to recognize patternsin electrical characteristics of the privacy glazing structure over timeand/or correlate electrical characteristics of the privacy glazingstructure with other data, such as ambient or structure temperaturedata. In some such examples, the driver can be configured toadjust/update one or more drive parameters for an electrical drivesignals according to the statistical analysis and recognized patternsand/or correlations. For example, the driver may be configured toautomatically switch between summer and winter electrical drive signalsbased on a recognized change in structure behavior over time.Additionally or alternatively, the driver can be configured to adjustone or more drive parameters based on received data, such as temperaturedata, based on an observed correlation between temperature data andstructure characteristics.

Electrical events, such a detected arcing event within the structure, apower surge, a power outage, a lightning strike, or other events cantrigger the driver to perform a characterization in order to detectchanges and/or damage to the structure.

In some examples, various electrical drive signal parameters can beadjusted based on tracked and/or measured data, such as aging dataand/or temperature data. In some embodiments, such parameters caninclude voltage (e.g., RMS voltage and/or a peak voltage), frequency,and/or a rise time/slew rate. In various examples, loading/updating oneor more drive parameters (e.g., step 912 in FIG. 9) comprises one ormore of:

-   -   decreasing a voltage value in response to a temperature increase    -   increasing a voltage value in response to a temperature decrease    -   increasing a voltage value as the structure age increases    -   decreasing a frequency value in response to a temperature        increase    -   increasing a frequency value in response to a temperature        decrease    -   decreasing a frequency value as the structure age increases    -   lengthening a slew rate/rise time in response to a temperature        increase    -   shortening a slew rate/rise time in response to a temperature        decrease    -   shortening a slew rate/rise time as the structure age increases.

Alternatively or in addition to factors such as aging andtemperature/seasonal changes in the operation of a privacy glazingstructure, other factors, such as a structure health metric, can beanalyzed. In some embodiments, a health metric includes a measure of aleakage current through the structure. Leakage current can result from aplurality of issues, such as breakdown in a structure material, such asoptically active material 18, a poor or breakdown coating, or othervolatile portion of a structure. Leakage current can be measured in avariety of ways. In an exemplary embodiment, a leakage current value canbe determined based on analysis of a current flowing through the privacyglazing structure during a particular time.

FIGS. and 10A and 10B show exemplary drive signal and resulting responsecurrent signal over time for a privacy glazing structure. As shown, aslew-rate square wave voltage applied to the privacy glazing structureresults in a periodic current response. While the signals are notnecessarily shown on the same scale in FIGS. 10A and 10B, it is apparentthat the shape of the current signal through the privacy glazingstructure is different between FIG. 10A and FIG. 10B. Such differencescan indicate changes in a leakage current flowing through the privacyglazing structure.

FIGS. 11A and 11B show zoomed-in views of the exemplary current andvoltage signals of FIGS. 10A and 10B, respectively, including differentdisplay scales for ease of display.

In some embodiments, one or more metrics associated with the currentsignal can be measured during a time when a structure is known to be ingood working condition, such as upon installation of the structure. Suchmetrics can include, for example, a time derivative or integral of themeasured current at or over a predetermined portion of the drive signal(e.g., during a positive voltage pulse, etc.). Additionally oralternatively, a difference in an equilibrium current during positiveand negative portions of the square wave (shown as Δ₁ and Δ₂ in FIGS.11A and 11B, respectively) can be used as a metric. For instance, insome embodiments, a measured current response to the applied electricaldrive signal comprises measuring a current response during apredetermined portion of the applied drive signal, such as a period oftime between transitions in an applied square wave. In some examples,this can avoid comparisons of current responses that include features(e.g., inrush currents) that may be present regardless of the conditionof the structure.

One or more current response metrics can be recorded over time in orderto determine one or more leakage current values associated with thestructure. FIG. 12 shows a process flow diagram showing an exemplaryprocess for determining one or more leakage current values. In someexamples, the method in FIG. 12 can be carried about via the driver of aprivacy glazing structure. The method includes measuring a valueassociated with a current response signal for a healthy structure at aninitial time t₀ (1200). Such measuring can include determining aderivative or integral of the current and/or a difference betweenequilibrium currents during positive and negative portions of an appliedalternating drive signal (e.g., a square wave). In some examples, timet₀ generally corresponds to a time when the structure is assumed to beat peak or near-peak health, such as during installation or initialoperation.

Next, the method includes again measuring a value associated with thecurrent response signal at a time t_(n) (1202), which, in a firstinstance after time t₀, may be denoted t₁ (n=1). For instance, in someexamples, the first measurement after the initial measurement at time t₀is performed at time t₁. The method includes determining a leakagecurrent at time t_(n) based on determined values associated with thecurrent signal at times t₀ and t_(n) (1204). For instance, in someexamples, determining the leakage current comprises determining thedifference in the measured value at time t_(n) vs. time t₀ in order todetermine the change caused by any leakage current that has developedsince the measurement of the value for the healthy structure at time t₀.In various examples, such determination can be performed locally, forexample via the driver, or can be done via cloud-based computing.

The method of FIG. 12 includes determining if the leakage currentsatisfies a predetermined condition (1206). If the leakage current doesnot satisfy the predetermined condition, the driver continues to applyan existing electrical drive signal (1208). For instance, in someexamples, the leakage current not satisfying the predetermined conditioncan indicate that there is no leakage current present or the leakagecurrent is small enough so that the existing electrical drive signal canadequately drive the privacy glazing structure without visible opticaldegradation. In some such cases, the drive signal does not need to bealtered to compensate for excess leakage current.

However, in some examples, if the leakage current does satisfy thepredetermined condition, the method can include the step of loadingand/or updating one or more drive parameters to establish an updatedelectrical drive signal (1210). For instance, in some examples, excessleakage current can degrade the optical performance of a privacy glazingstructure, but can be compensated for via adjustments to the electricaldrive signal.

Example adjustments to an electrical drive signal based on excessleakage current can include increasing a voltage (1212), decreasing afrequency (1214), and/or pulsing a voltage (1216). In some examples,increasing a voltage (e.g., the value of V_(A) in FIG. 4) can compensatefor lost voltage due to the leakage current. Decreasing frequencyprovides additional time for a capacitive optically active material tocharge, for example, during a positive portion of a square wave drivesignal. In some examples, decreasing a frequency of the electrical drivesignal comprises increasing a period of the electrical drive signal. Forinstance, with respect to the example electrical drive signal shown inFIG. 4A, adjusting an electrical drive signal comprises increasing theamount of time that the voltages V_(A) and −V_(A) are applied duringeach cycle.

With respect to voltage pulsing, in some examples, a drive signalincludes one or more floating steps, in which the optically activematerial is disconnected from power and ground. For instance, withrespect to FIG. 5, in some examples, a drive signal can include a periodof time during which, for example, all switches SW1, SW2, SW3, and SW4are opened so that the load (e.g., the optically active material betweencontact electrodes) maintains its current voltage. However, leakagecurrent may cause the voltage at the load to sag during the floatingstep. Pulsing the voltage (e.g., step 1216) can include modifying theelectrical drive signal to include applying one or more voltage pulsesto the load during one or more floating steps in order to maintain avoltage at the load and compensate for voltage sagging due to leakagecurrent. In an example implementation, a drop in voltage from anexpected value (e.g., a voltage sag) across the structure can bemeasured and compared to a predetermined threshold. If the drop in thevoltage meets or exceeds the predetermined threshold, a rail voltagepulse can be applied to the load. The frequency of applying the railvoltage pulse can depend on the severity of the sag (e.g., due to theseverity of a leakage current). For example, in some cases, the railvoltage pulse can be applied multiple times in a single cycle or halfcycle of the applied electrical drive signal.

In various embodiments, the index n can be incremented, and steps in theprocess of FIG. 12 can be repeated for a plurality of times t₁, t₂, . .. , t_(N). In some examples, measured values and/or leakage currentvalues associated with one or more times (e.g., at any one or more oftimes t₀ . . . t_(N)) can be saved to memory. Additionally oralternatively, the method can include generating a measurement curve ofthe measured leakage current vs. time and/or vs. index. In someexamples, a trend of leakage current over time can be used to determineinformation regarding a likely cause of the leakage current.

In some embodiments, determining if the leakage current satisfies apredetermined condition (e.g., step 1206) can include determining if asingle leakage current value satisfies a condition, such as a determinedleakage current exceeding a threshold leakage current value or fallingwithin a predetermined range of leakage current values. Additionally oralternatively, determining if the leakage current satisfies apredetermined condition can include determining if a trend of leakagecurrent vs. time and/or time index satisfies a predetermined condition,such as if the derivative of the leakage current over time exceeds apredetermined threshold.

In some embodiments, one or more actions can be taken in response to theleakage current satisfying a predetermined condition, such as shown insteps 1212, 1214, and 1216. In some instances, different such actions orcombinations thereof can be performed in response to different leakagecurrent conditions, such as a leakage current value falling intodifferent predetermined ranges and/or a leakage current trend over timesatisfying one or more predetermined conditions. In some embodiments,leakage current compensation can be initiated and/or modified by a userin the event that the privacy glazing structure has optically degraded.

In some examples, non-linearities in the current response with respectto an applied voltage can be attributed to ion behavior in the privacyglazing structure. In some such examples, such non-linear responses canbe analyzed to determine various parameters, such as various sizesand/or densities of ions moving in the structure and the response ofsuch ions to the applied electric field in the structure. In someembodiments, such information can be used to determine details regardingthe optically active material and how such material is breaking downduring operation causing optical degradation of the privacy glazingstructure. In some embodiments, data of leakage current over time can beused to determine one or more leakage current sources, such as badcoatings, ion generation, and/or other factors.

Various such calculations and/or determinations can be performedlocally, for instance, via the driver, and/or can be performed in anexternal environment, such as via cloud-based computing.

As described with respect to FIG. 6, a single driver 300 can beconfigured to provide electrical drive signals to each of a plurality ofprivacy glazing structures (e.g., 310, 320, 330) for simultaneousoperation of such structures. As described herein, a driver can beconfigured to determine electrical characteristics of a privacy glazingstructure in order to establish an electrical drive signal appropriatefor driving such a structure. In some embodiments, a driver can beconfigured to perform various such processes (e.g., as shown in FIGS. 7,9, and/or 12) for each of a plurality of associated privacy glazingstructures. A driver can be configured to determine an appropriateelectrical drive signal for each of a plurality of privacy glazingstructures, and provide such electrical drive signals to each suchprivacy glazing structure simultaneously.

As described elsewhere herein, in some examples, the electrical drivesignal comprises a square wave or an approximately square wave (e.g., asquare wave having a slew rate, a trapezoidal wave, a square wave shapehaving a slow zero-crossover, etc.) signal. For instance, the exemplaryvoltage vs. time drive signals shown in FIGS. 4, 10A, and 10B show anapproximate square wave drive signal. Further, as shown in FIGS. 10A and10B, transitions that occur every half-period in the square wave drivesignal results in a spike in the current through the structure. Ingeneral, given a capacitive privacy glazing structure, the steeper theedge of the square wave drive signal, the larger the correspondingcurrent spike is likely to be. Thus, if a plurality of privacy glazingstructures are being driven simultaneously with square wave orapproximate square wave drive signals, current spikes in each structuremay occur at approximately the same time, creating a large current/powerpeaks output from the driver.

In some embodiments, the driver is configured to stagger the electricaldrive signals applied to one or more privacy glazing structures toreduce the peak current/power draw associated with the current responseto the applied electrical drive signals. Put differently, staggering theelectrical drive signals can be done so that the peak current drawn byeach of the privacy glazing structures driven by the driver occurs atdifferent times. In some embodiments, staggering a second electricaldrive signal with respect to a first electrical drive signal comprisesdelaying the application of the second electrical drive signal withrespect to the application of the first electrical drive signal when thefirst and second electrical drive signals are in phase with one another.In some examples, staggering a second electrical drive signal withrespect to a first electrical drive signal comprises applying the firstand second electrical drive signals substantially simultaneously whilephase-shifting the second electrical drive signal relative to the firstelectrical drive signal. In still further embodiments, staggering asecond electrical drive signal with respect to a first electrical drivesignal comprises phase shifting the second electrical drive signal withrespect to the first electrical drive signal and temporally delaying theapplication of the second electrical drive signal with respect to theapplication of the first electrical drive signal. Thus, in variousembodiments, staggering electrical drive signals can includephase-shifting a signal, temporally delaying the application of asignal, or combinations thereof.

FIG. 13 shows a process flow diagram showing an example process forapplying staggered electrical drive signals to a plurality of privacyglazing structures. The method includes applying an electrical sensingpulse to each of a plurality of privacy glazing structures (1300) anddetermining an electrical drive signal for each of the plurality ofprivacy glazing structures (1302). Such steps can be performed for eachof the privacy glazing structures, for example, as described withrespect to FIG. 7.

The method of FIG. 13 further includes determining a stagger amount forone or more of the privacy glazing structures (1304). Such determiningcan be performed in a variety of ways. In some examples, the driver canbe configured to provide a predetermined amount of delay between theelectrical drive signals for each privacy glazing structure.Additionally or alternatively, in some examples, the driver can beconfigured to analyze the determined plurality of electrical drivesignals in order to determine an appropriate amount of stagger forapplying the plurality of electrical drive signals. For instance, one ormore parameters of each electrical drive signal, such as magnitude,frequency, and the like, can be analyzed to determine an appropriateamount of stagger between the electrical drive signals, for example, toreduce instances of signal superposition that can result in largecurrent and/or power spikes. In some embodiments, frequency content of afirst electrical drive signal and a second electrical drive signal canbe compared in order to determine an offset between the first and secondelectrical drive signals to reduce or eliminate superposition of one ormore features of the drive signals, such as transitions between statesin square wave drive signals.

In some examples, each of the plurality of electrical drive signals forthe corresponding plurality of privacy glazing structures is staggeredwith respect to the other signals so that no two signals are appliedsimultaneously. In other examples, the driver may determine that two ormore electrical drive signals can be applied simultaneously withoutresulting in an undesirable current spike (e.g., resulting in a totalcurrent draw, such as a peak current draw, exceeding a predeterminedthreshold). In some such examples, the driver can be configured toprovide such electrical drive signals simultaneously while potentiallystaggering other electrical drive signals.

The method of FIG. 13 further includes applying an electrical drivesignal to each of the plurality of privacy glazing structures includingthe determined stagger amounts (1306). Including the stagger amounts inapplying an electrical drive signal can include delaying the applicationof a determined electrical drive signal and/or phase-shifting theelectrical drive signal. As described, in some cases, determined staggeramounts can result in multiple electrical drive signals (e.g., a subsetof a plurality of applied electrical drive signals) being applied tocorresponding privacy glazing structures simultaneously and in-phasewith one another while other signals are staggered with respect to thesimultaneously-applied signals. In other examples, each electrical drivesignal is delayed and/or phase-shifted with respect to each of the otherelectrical drive signals.

In some embodiments, the driver can be configured to adjust one or moreelectrical drive signals in order to better stagger such signals. Forinstance, as represented by the broken lines in FIG. 13, a driver can beconfigured to determine a stagger amount (1304) based on adjustedelectrical drive signals (e.g., different electrical drive signals thandetermined via the method of FIG. 7). Thus, in some such embodiments,the driver can be configured to determine updated electrical drivesignals (1302) after determining appropriate stagger amounts to reducepeak current and/or power loads on the driver. In an exemplaryembodiment, if a first privacy glazing structure is to be driven with anelectrical drive signal having a first frequency and a second privacyglazing structure is to be driven with an electrical drive signal havinga second frequency different from the first. Staggering such signals bya phase shift and/or delay may reduce the current spikes associated withthe initial application of the respective electrical drive signals.However, superposition of such electrical drive signals may neverthelessresult in times at which undesirably large current and/or power spikesoccur. In some examples, the driver can be configured to adjust one orboth such electrical drive signals to reduce or eliminate suchinstances, such as adjusting the electrical drive signals to include acommon frequency and/or adjusting the magnitude of one or both signalsso that combined current and/or power spikes remain below a thresholdlevel. Other techniques for adjusting one or more electrical drivesignals for corresponding one or more privacy glazing structures inresponse to staggering analysis are possible. In some such examples,upon adjusting one or more such electrical drive signals to reduceinstances of undesirably large current and/or power spikes, thedetermined electrical drive signals including the determined staggeramounts can be applied to respective privacy glazing structures (1306).

FIGS. 14 and 15 show example implementations of applying electricaldrive signals including determined amounts of stagger to a plurality ofprivacy glazing structures. FIG. 14 shows a driver 1400 in electricalcommunication with privacy glazing structures 1410, 1420, and 1430. Inthe illustrated example of FIG. 14, a driver 1400 provides a commonelectrical drive signal f(t) to each of privacy glazing structure 1410,1420, and 1430. For example, each privacy glazing structure 1410, 1420,and 1430 could be the same type of structure, include similar electricalcharacteristics, or the like, in order to result in the same generalelectrical drive signal to be applied to each structure, such asdetermined via the method of FIG. 7.

As shown in FIG. 14, the electrical drive signal f(t) is phase-shiftedbetween each privacy glazing structure to reduce or eliminate currentspikes at each structure simultaneously. For instance, while signal f(t)is provided to privacy glazing structure 1410, signal f(t−Δt) is appliedto privacy glazing structure 1420. Thus, various elements of theelectrical drive signals and the resulting current response (e.g.,current spikes) will be delayed by an amount Δt in privacy glazingstructure 1420 with respect to privacy glazing structure 1410.Similarly, signal f(t−2Δt) is applied to privacy glazing structure 1430,such that elements of the electrical drive signal and resulting currentresponse will be delayed by Δt in privacy glazing structure 1430 withrespect to privacy glazing structure 1420, and by 2Δt with respect toprivacy glazing structure 1410.

In some examples, the amount of stagger between each of the plurality ofelectrical drive signals is within one period of the electrical drivesignal. For example, if the system in FIG. 14 includes privacy glazingstructures 1410, 1420, and 1430, and electrical drive signal f(t) isperiodic with a period of T, in some instances, 2Δt<T. For instance, ifthe frequency of the electric drive signal f(t) is 60 Hz, then in someexamples, Δt<8.3 ms. In still further examples, the amount of staggerbetween each of the plurality of electrical drive signals is within ahalf period of the electrical drive signal.

FIG. 15 shows a driver 1500 providing electrical drive signals to eachof a plurality of privacy glazing structures 1510, 1520, and 1530. Asshown, in some examples, different electrical drive signals f(t), g(t),and h(t) can be provided to the privacy glazing structures 1510, 1520and 1530, respectively. Such electrical drive signals can be determinedfor each privacy glazing structure, for example, via the method shown inFIG. 7. Different electrical drive signals can include one or moredifferent parameters, such as peak voltage, slew rate, wave shape,frequency, and the like. As described elsewhere herein, in someexamples, the driver can determine an amount of stagger to apply betweendifferent electrical drive signals, for example, based on mathematicalanalysis of the determined electrical drive signals. In the illustratedexample, the electrical drive signal g(t) applied to privacy glazingstructure 1520 is staggered with respect to electrical drive signal f(t)by an amount Δt₁ and the electrical drive signal h(t) applied to privacyglazing structure 1530 is staggered with respect to electrical drivesignal f(t) by an amount Δt₂. In various examples, Δt₁ can be greaterthan, less than, or equal to Δt₂ according to the determined amount(s)of stagger based on the determined electrical drive signals. Asdescribed elsewhere herein, in some examples, different electrical drivesignals can be applied simultaneously (e.g., Δt₁=0, Δt₂=0, and/orΔt₁=Δt₂) if the driver determines that the combined current response tosuch electrical drive signals would not amount to an undesirably largecurrent and/or power spike (e.g., greater than a predeterminedthreshold), for example, due to certain load sizes provided by aplurality of such privacy glazing structure.

FIGS. 16A-16C show example voltage vs. time profiles for a plurality ofelectrical drive signals used to drive a corresponding plurality ofprivacy glazing structures in a system. FIG. 16A shows a function f(t).FIG. 16B shows function f(t) delayed by a time Δt, such that theresulting signal can be represented by f(t−Δt). Similarly, FIG. 16Cshows function f(t) delayed by a time 2Δt, such that the resultingsignal can be represented by f(t−2Δt). In the illustrated example ofFIGS. 16A-16C, an electrical drive signal f(t) is applied to separateprivacy glazing structures with incorporated staggering so that varioustransition portions of each electrical drive signal that may causeindividual current and/or power spikes do not happen simultaneously.

In some embodiments, once a plurality of drive signals are determined,the driver can determine which electrical drive signals, when appliedsimultaneously, cause one or more parameters (e.g., current spikevalues) to exceed a predetermined threshold. Similarly, the driver candetermine which electrical drive signals, when combined, do not causethe one or more parameters to exceed the predetermined threshold(s). Thedriver can determine which electrical drive signals can be appliedsimultaneously and stagger the application of electrical drive signalsor groups of electrical drive signals such that the one or moreparameters do not exceed the predetermined threshold(s) when eachelectrical drive signal or group of electrical drive signals areapplied.

In an example embodiment, a driver is connected to power five privacyglazing structures, three of which represent a maximum load that can bedriven by the driver. The remaining two privacy glazing structures areconsidered small, and can be driven simultaneously without anyelectrical parameters exceeding a predetermined threshold. The drivercan be configured to provide electrical drive signals to the two smallerloads simultaneously and in phase with one another, while staggeringdelivery of each of the remaining three electrical drive signals to theremaining structures.

While shown in FIGS. 14, 15, and 16A-C as including three privacyglazing structures, in general, systems can include a driver and anynumber of privacy glazing structures in communication therewith. Thedriver can be configured to perform various processes described hereinfor each of one or more privacy glazing structure in electricalcommunication therewith. In some examples, the driver can be configuredto determine the number of privacy glazing structures to be providedwith electrical drive signals. Such a determination can be used indetermining various information, such as determining appropriateelectrical drive signals and/or staggering amounts for driving the oneor more privacy glazing structures.

Drivers can be configured to carry out processes as described herein ina variety of ways. In some examples, a system driver can include one ormore components configured to process information, such as electricalsignals and/or other received sensor information, and perform one ormore corresponding actions in response thereto. Such components caninclude, for example, one or more processors, application specificintegrated circuits (ASICs), microcontrollers, microprocessors,field-programmable gate arrays (FPGAs), or other appropriate componentscapable of receiving and output data and/or signals according to apredefined relationship. In some examples, the driver can include orotherwise be in communication with one or more memory components, suchas one or more non-transitory computer readable media programmed withinstructions for causing one or more such components to carry out suchprocesses. Additionally or alternatively, the driver can communicatewith additional devices, such as external computer systems and/ornetworks to facilitate information processing, such as cloud-basedcomputing.

Various non-limiting examples have been described herein. Those havingordinary skill in the art will understand that these and others fallwithin the scope of the appended claims.

The invention claimed is:
 1. A method for assessing and adapting tochanging characteristics of an electrically controllable optical privacyglazing structure comprising: applying an electrical drive signal to aprivacy glazing structure comprising an electrically controllableoptically active material to control an optical state of theelectrically controllable optically active material; measuring anelectrical characteristic of the privacy glazing structure indicative ofa health of the privacy glazing structure at a first time; measuring theelectrical characteristic of the privacy glazing structure indicative ofthe health of the privacy glazing structure at a second time later thanthe first time; detecting a change in the electrical characteristicbased on the electrical characteristic measured at the second time andthe electrical characteristic measured at the first time, the change inthe electrical characteristic indicating a change in the health of theprivacy glazing structure; and in response to detecting the change,adjusting at least one parameter of the electrical drive signal providedto the privacy glazing structure to compensate for the change in thehealth of the privacy glazing structure.
 2. The method of claim 1,further comprising: determining a leakage current value associated withthe privacy glazing structure at the second time based on the detectedchange in the electrical characteristic of the privacy glazingstructure; wherein adjusting the at least one parameter of theelectrical drive signal is performed if the determined leakage currentsatisfies a predetermined condition.
 3. The method of claim 2, furthercomprising measuring the electrical characteristic of the privacyglazing structure indicative of the health of the privacy glazingstructure at plurality of additional times later than the first andsecond times; and determining the leakage current value associated withthe privacy glazing structure at each of the plurality of additionaltimes; and determining a trend in the leakage current over time.
 4. Themethod of claim 3, wherein determining a trend in the leakage currentover time comprises determining a temporal derivative of the leakagecurrent.
 5. The method of claim 4, further comprising adjusting at leastone parameter of the electrical drive signal in response to the temporalderivative of the leakage current satisfying a predetermined thresholdcondition.
 6. The method of claim 1, further comprising measuring theelectrical characteristic of the privacy glazing structure indicative ofthe health of the privacy glazing structure at plurality of additionaltimes later than the first and second times; comparing the electricalcharacteristic at each of the plurality of times to the electricalcharacteristic at the first time; and if, at any of the plurality oftimes, the electrical characteristic differs from the electricalcharacteristic at the first time by more than a threshold amount,adjusting at least one parameter of the electrical drive signal.
 7. Themethod of claim 1, wherein measuring the electrical characteristiccomprises measuring a current response to the applied electrical drivesignal.
 8. The method of claim 7, wherein measuring the current responseto the applied electrical drive signal comprises measuring the currentresponse to a predetermined portion of the applied electrical drivesignal.
 9. The method of claim 8, wherein the applied electrical drivesignal comprises a square wave electrical drive signal, and wherein thepredetermined portion of the applied drive signal comprises a period oftime between transitions in the square wave drive signal.
 10. The methodof claim 7, wherein measuring the current response to the appliedelectrical drive signal comprises calculating at least one of anintegral and a derivative of the current over time.
 11. The method ofclaim 1, wherein the adjusting the one or more parameters of theelectrical drive signal comprises at least one of: increasing a voltage,decreasing a frequency, and adding one or more voltage pulsing steps tothe electrical drive signal.
 12. The method of claim 1, whereinmeasuring an electrical characteristic of the privacy glazing structureindicative of the health of the privacy glazing structure comprisesmonitoring the current flowing through the privacy glazing structurewhile a voltage applied to the privacy glazing structure is heldconstant.
 13. The method of claim 1, further comprising performing anion density measurement and at least one of predicting and determining acause of failure based on the ion density measurement.
 14. The method ofclaim 13, wherein the privacy glazing structure comprises a liquidcrystal material, and wherein the detected change in the electricalcharacteristic is due to a chemical change of the liquid crystalmaterial.
 15. The method of claim 1, wherein the electricallycontrollable optically active material comprises a liquid crystalmaterial.
 16. The method of claim 1, wherein the health of the privacyglazing structure is indicative of a degradation state of theelectrically controllable optically active material of the privacyglazing structure.